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A261617
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Numbers n such that n!!! + 3^n is prime.
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0
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0, 2, 16, 17, 20, 22, 28, 31, 37, 40, 53, 65, 71, 73, 82, 124, 130, 187, 203, 266, 308, 326, 386, 502, 662, 1919, 3136, 3229, 4640, 8113, 8659, 12307, 20972, 26408, 49391
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OFFSET
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1,2
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COMMENTS
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n!!! is the triple factorial sometimes written n!3.
a(36) > 50000.
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LINKS
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EXAMPLE
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2 is in the sequence because 2!!!+3^2 = 2+9 = 11 is prime.
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MATHEMATICA
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MultiFactorial[n_, k_] := If[n < 1, 1, If[n < k + 1, n, n*MultiFactorial[n - k, k]]];
Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 3] + 3^#] &]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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